DJ Reader could miss the Lions’ season opener.

The Detroit Lions signed DJ Reader to their defensive line during free agency, hoping he would fill the gap at nose tackle.

However, Reader is recovering from a torn quadriceps injury and has not yet practiced with the Lions after one week of training camp. According to a report from MLive, Reader is unsure if he will be ready for the team’s regular-season opener on September 8.

“I don’t know about that,” Reader told MLive’s Kyle Meinke. “I’m just working hard. We’ll see.”

Lions coach Dan Campbell has made it clear that Reader’s recovery timeline has not surprised the coaching staff. At the end of organized team activities, Campbell mentioned that he anticipated the defensive tackle might not be ready for the start of training camp.

Currently, Reader is the only Lions player on the Physically Unable to Perform list, although Campbell stated he is healthy. The team is being cautious as he continues his rehabilitation.

“I feel great,” Reader said, according to MLive. “I’m just out there working and feeling good. Just trying to regain some strength. It’s part of the rehab process these days. I’ve been through it before. There are days when you feel great and some days when it’s not as good. But overall, it’s been good. I’m on the mend and haven’t had any setbacks.”

The Lions will begin padded practices on Monday and are just a week away from traveling to New York for joint practices with the Giants.